Thermostat control mechanism for heating systems



G. W. CRISE Aug. 19, 1947.

Filed lay 27. 1945 Patented Aug. 19, 1947 THERMOSTAT CONTROL MECHANISMFOR HEATING SYSTEMS George W. Crise, Columbus, Ohio, assignor to CriseManufacturing Company, Columbus, Ohio, a corporation of Ohio ApplicationMay 27, 1943, Serial No. 488,708

7 Claims.

This invention relates to thermostatic switch mechanism. havingparticular reference to automatic control means of the type employed ingoverning the operation of ,electrically actuated means used inautomatic or semi-automatic heating systems,

One of the objects of the invention is to provide a simple, efficientand inexpensive system involving automatically operating thermostaticcontrols which, when employed in connection with a furnace or otherheating system, will provide well-regulated operation of such a furnaceor heating system under widely fluctuating temperature or weatherconditions and without requiring the aid of manually performed seasonaladjustments.

It is well recognized in the art that conventional types of domesticfurnace controls, if properly adjusted for cold weather operation,permit overheating of the house in mild weather or, conversely, ifproperly adjusted for mild weather, are apt to produce underheating ofthe house in cold weather. A

This difficulty results principally from the time lag required for theheat from the fire within the furnace to reach the controlling,room-positioned, thermostat. The application of localized electric heatat the room thermostat to shorten the running cycle of the furnacereduces the problem of overheating, but if used to a suillcient extentto eliminate the dilculty in very mild weather, it oftens causes theroom thermostat to shut off the heat supply before any substantialeffect of the increased furnace fire reaches the thermostat. Such actionduring cold weather tends to shut off the heat supply shortly after itis started, with the result that the drafts, stoker, gas or oil burnerare caused to `operate in short intermittent cycles, thus producing areduction in heat generation as a result of such part time operation.

The first-mentioned system of supplying artificial heat by means of anelectric preheater disposed in the room thermostat is satisfactory formild weather, providing the action is not so rapid as to cause heatingcycles of objectionably short duration. However, this preheater actionshould be modied to allow longer operating" cycles in cold weather.Therefore, in accordance with the present invention, I provide animproved compensating type of room thermostat having a sectionalpreheater, which operates in response to substantial changes in furnacetemperature, such as that produced by warm and cold weather heatingconditions, to vary the effect of the preheater on the thermostat. Th'ecircuit changing of the preheater, to release more or less heat, isaccomplished by a multiple contact furnace thermostat, the latterfunctioning automatcally to enable the preheater within the roomthermostat to produce its full capacity of heat or partial capacitydepending upon the operating temperatures of the atmosphere adjacent tothe furnace. n

While the combination of the furnace thermostat and the selectivepreheating room thermostat gives generally satisfactory service for theaverage furnace installation, it is not entirely adequate to controlsuch abnormal conditions as those resulting from a sudden change from acold house to normal room temperature or upon widely iluctuating outdoortemperatures, since in the case of large heat storage capacity heatingsystems, such as steam or hot water, enough heat may be stored in thecirculating fluid to cause overheating before the house temperatureapproaches the setting of the room thermostat. Such conditions occurfrequently with clock-controlled thermostats which allow cooling of thehouse during certain hours of th'e night.

Under these conditions, an adequate solution' is to limit the furnace orwater temperature so that only sufficient heat is generated to bring thehouse to proper temperature, and for this purpose the thermostat locatedin or adjacent to the furnace is used. However, to be effective inmild.weather, the furnace-located thermostat must be set to throttle thefire at a fairly low temperature, and this low temperature tends toprevent the furnace from providing adequate heat for cold weather. Tocompensate for this latter condition, the present invention furtherprovides, in association with the room and furnace thermostats, animproved outdoor thermostat, by means of which the operation of the roomand furnace thermostats is modified to adapt the system to the heatdemands occasioned by changes in temperatures outside the house equippedwith the system.

Accordingly, my improved system in a preferred application comprisesthree thermostatic units, namely, a compensating room thermostatprovided with variable preheater, a multiple contact furnace thermostatand an out-of-doors thermostat, the latter functioning to change theoperating range of the selective furnace thermostat according toexternal weather conditions, and at the same regulating circuits on theroom thermostat to impart to its heating system a short operating cyclein warm weather and a longer cycle in cold weather.

For a further understanding of th'e invention, reference is to be had tothe following description and the accompanying drawing, wherein:

Fig. l is a diagrammatic view disclosing a house heating system providedwith the improved thermostatic controls constituting the presentinvention;

Fig. 2 is a similar view disclosing the use of a relay for governing theoperation of the furnace controls in lieu of the shaded pole inductionmotor set forth in Fig. 1:

Fig. 3 is a group view illustrating the action of the furnacethermostat, showing the latter in its different positions of operation;

Fig. 4 is a fragmentary detail sectional view through the outdoorthermostat.

Referring more particularly to the drawing.'

the numeral I designates a standard coal burning furnace, shown asprovided at its bottom with a pivoted draft door 2. In effecting theoperation of this door, use may be made of a shaded pole induction motor3 of the type set forth in my prior patent, No. 2,134,685, datedNovember l, i938. The amature shaft 4 of this motor is employed to drivea wheel 5 about which is trained a cable 5, one end of said cable beingconnected with the door 2 while its other end may be provided with acounterbalancing weight 1.

The motor l commises a laminated held frame I formed with slotted poles.said frame being energized by a primary coil 9 connected to analternating current source I0. One pair of the poles of said frame isequipped with a set ofv small closed shading coils I I and I2 ofsufilcient current capacity to cause a partial phase splitting,producing counter-clockwise rotation of the armature Il by theconventional shading coil method. Wound shading coils Il and I5 aremounted upon the second pair of poles, these wound coils being connectedin series and possessing suiliciently larger capacity to overpower theeffect of the coils I I and I2 and to cause reverse phase splitting andconsequent motor reversal when their circuit is closed. 'Ihermostaticcontrols, hereinafter described in detail, are employed for governingthe opening and closing of the circuit or circuits in which the coils Iland I5 are disposed.

It will be clear from an inspection of the drawing that when the circuitto the coils I4 and I5 is open, the latter coils are rendered inactiveand the direction of rotation of the motor will be determined by theaction of the closed shading coils II and l2. the counter-clockwiserotation closing the furnace drafts so that when the coils Il and I5 areenergized, the relatively larger capacity thereof becomes operative,causing the motor to rotate in a clockwise direction opening the draftsand overcoming the action of the coils II and I2, producing a reversephase splitting. The motor thus operates to raise and lower the draftdoor and thereby controls the rate of fuel combustion within the furnaceI.

The features of the present invention are applicable to all thewell-known types of domestic heating systems, such as gas or oil firedburners, mechanical coal stokers and the like. The reversible inductionmotor shown in Fig. l operates satisfactorily when draft door, dampersand check devices are to be automatically operated. When, however, thesystem is used in connection with heating systems employing a motordriven stoker, an oil burner or motor valve. in lieu of using theinduction motor I may substitute therefor an ordinary relay as disclosedat I6 in Fig. 2, said relay being Joined with the current source I0 bymeans of conductors I1. Associated conductors I8 lead from the relay tothe motor of the stoker, oil burner or motor valve, and a third set ofconductors I9 extend from the magnet of the relay to the thermostaticcontrols of the present invention.

The present invention resides primarily in the employment of a.plurality of cooperative thermostatic switches for governing theoperation of electrical or mechanical furnace equipment of the typeabove set forth. My system involves first the use of a compensating roomthermostat indicated generally by the numeral 20; second, a furnacethermostat 2I located on, in or immediately adjacent to the associatedfurnace or other heating system so that it is responsive to theoperating temperatures of the furnace or heating system, and, third, anoutdoor thermostatic switch 22, all three switches being interconnectedand adapted for the automatic control of an associated electricalappliance, such as the motor i 3 or the relay I6 and their associatedfurnace equipment.

The room thermostat as here disclosed comprises a bimetallic element 23.the latter having its fixed end attached to an axially movable stud 24carrying a crank arm 25. The outer end of the arm 25, in a preferredform of my invention, may be linked as at 26 with the arm 21 of a clockmechanism 28. The free end of the bimetallic element carries an armature28 which is spaced from the poles of a permanent magnet III. Also, thefree end of the bimetallic element carries a contact 3l which is adaptedto be brought into and out of engagexiient with an adjustable contact 32comprising one end of a manually adjustable screw 33. the latter beingreceived within a threaded bore provided in a fixed terminal post 34. Itwill be understood that the clock mechanism 2B may or may not be used.

Mounted contiguously to the bimetallic element 23 of the room thermostatis a resistance unit 35, which is known in the art as a'preheater. Thisresistance unit consists of separately or collectively energlzablesections, indicated by the numerals 35a, 35h and 35e, which may be inwhole or in part disposed within a heat-storing metallic conduit 38. Bythe use of thermostatic means. hereinafter described in detail, thevarious sections of this resistance unit may be energiaed automatically,thus varying the heat effect exerted thereby on the element 23. Since,as hereinafter more fully explained, the current flowing through thesesections of resistance is substantially constant under all conditions,the total amount of heat generated varies in proportion to the number ofsections in circuit. For example, if only the section shown at 55a isenergized, the relatively small amount of heat 4liberated thereby causesthe element 23 to respond slowly. so that electrical apparatus joinedwith the thermostat 20 will have long active operating cycles betweenperiods of inactivity. If the section 35h is energized in connectionwith the section 35a, a greater amount of heat will be liberated by theresistance unit, so that the operating cycle of the equipment controlledby the thermostat 25 will be of medium duration. If all three sections,35a, 35h and 25e, of the preheater or resistance unit are simultaneouslyenergized, a maximum amount of heat will be liberated so that theoperating cycles will be of shortest duration. as. for example, in mildweather operation.

To obtain this variable control of the heat liberated by the resistanceunit 35 of the room thermostat,lI employ in combination therewith, thefurnace thermostat 2I and. preferably, the outdoor thermostat 22.

In one of its preferred forms, the furnace thermostat comprises asupport 4I, shown in the drawings as being arranged immediately abovethe bonnet of the furnace I, The support 4I has secured thereto thefixed end of a bimetallic warping bar or an equivalent flexing element42, the latter being so formed that its free end deflects upwardly asthe furnace cools and downwardly as the temperature around the furnaceincreases. The free end of the element 42 carries a spring steel reed43, and mounted upon this reed is a plurality of spaced contactsdisclosed at 44, 44a and 44h. These contacts are adapted forregistration with the ends of manually adjustable contact-forming screws`46, 46a and 4Gb, the latter being shown as positioned in the threadedbores of terminal posts 46a, 48h and 48o, respectively.

The adjustment provided by the screws 46, 46a and 46b and the flexingcharacteristics of the bar 42 and the reed 43 are such as to causeseparate engagement'of the contacts 44, 44a and 44h with theirrespective contact-forming screws. As the bar 42 cools and begins upwarddeflection, the contact 44 first makes engagement with the contact screwI46. Continued upward movement of the bar 42 brings the contact 44a intoengagement with the contact screw 46a, flexing the reed 43 by a rollingaction which removes the contact 44 from engagement with the screw 46.Further upward movement of the thermostatic bar 42 then brings thecontact 44h into engagement with the screw 46h, and releases theengagement between contacts 44a and screw 46a. The reverse of theseoperations takes place as the temperature around the bar 42 isincreased.

Leading from the post 48 is a, conductor 49 which extends to theterminal post I) of the outdoor thermostat 22. A second conductor 5Ileads from the terminal post 48a to the terminal post 52 of the outdoorthermostat. The posts 50 and 52 are arranged in spaced relation and theycarry adjustable contact-forming screws 53 and 54 respectively. Abovethe screws 53 and 54, the outdoor thermostat 22 includes a bimetallicwarping element 55 which has the fixed end thereof mounted on a support56. The outer end of the element I55 carries a spring strip 51, andattached to the outer end of this spring strip is a block of insulatingmaterial 58. Carried by this block is a contact 59 which is adapted forengagement with the upper end of the screw 54. The characteristics ofthe warping `element are such that as the ambient temperature increases,the element deflects upwardly, th! movement thereof bein-gf`l` inopposition to that of the bimetallic element 42.

From the contact 59, a conductor 60 leads to the preheating unit 35 ofthe room thermostat, the end of the conductor 60 joining the preheaterbetween the sections 35h and 35e thereof. Another conductor 6I leadsfrom the fixed end of the warping element 55 to the preheater, joiningthe latter between its sections 35a and 35h, `A

third conductor 62 leads from the terminal post 48h to the outerterminating end of the preheater" section 35o, thus completing thecircuit connections between the room, furnace and outdoor thermostats. Aconductor 63 extends from the shaft 24 of the room thermostat to thewound shading coil I4 of the motor 3, or the conductor 63 the conductorsI9 of the relay I6, shown in Fig. 2. Another conductor 64 leads from thesecond of the wound shading coils to the thermostatic bar 42, or theconductor 64 may constitute an extension of one of the leads I9 of therelay I6.

In operation, if the temperature Iadjacent the furnace thermostat shoulddecline to a predetermined degree, the bar 42 deects upwardly from theposition shown at the upper. left of Fig. 3 to the position disclosed atthe lower left of Fig. 3, in which the contact 44 engages the contactscrew 46. At this time current from source I0, passing through primarywinding 9 of motor 3, induces current in the coils I4 and I5. Thispasses from coil I5 by way of conductor 64, bar 42, reed 43, contact 44,screw 46 to conductor 49. If the outdoor temperature surrounding the4thermostat 22 is sufliciently low to have flexed the element downwardlyuntil it contacts with the screw 53, current will then pass throughelement 55, conductor 6I to the section 35a of the preheating resistor.

In the event the temperature around the room thermostat 20 has decreasedsufliciently to bring contact 3| into engagement with screw 32, currentafter passing through the section 35a of the preheater will pass throughscrew 33, contact 3|, bimetallic element 23, and conductor 63 to thereturn side of the coil I4 of the motor 3, or the relay I6, therebyenergizing the motor 3 or said relay to effect the operation ofassociated furnace or heater controls. It will be understood that thecombined resistance of the coils I4 and I5 is relatively high ascompared with that of the heater sections, so that the current flowingremains substantially the same regardless of the number of sections incircuit. There fore, under the conditions just described, the operatingcycle of such controls will be comparatively long, since only thesection 35a of the preheater has been energized and a minimum value ofheat liberated thereby. If the outdoor temperatures are Such as to notjustify operation on the part of the system, the bimetallic element 55remains in spaced relation from the contact screw 53, thereby keepingthe circuit V Open.

In the event the outdoor temperature is such 'that the element 55 doesnot deflect downwardly may be extended to form a continuation of one ofto cause its engagement with the screw 53, and yet the temperaturearound the furnace thermostat continues to decrease, the bar 42 willdeflect upwardly to a greater degree to assume the position disclosed inthe upper right of Fig. 3, in which the contact 44a engages with lthescrew 46a and breaks engagement between Contact 44 and screw 46. Underthese conditions, current will pass from the source I0, through motor 3,conductor 64, bar 42, reed 43, contact 44a, screw 46a to the conductor5I. The latter conductor leads to the terminal post 52. carrying thescrew 54 which is maintained in constant engagement, irrespective of theflexure of the element 55, with the contact 59, current passing fromcontact 59 through conductor 60 to the outer end of the pre heatersection 35h. Current then flows through section 35h and section 35a ofthe preheater in series, and if the room thermostat is closed, thecurrent will then travel through the latter and back to the motor 3 ortherelay I6. Due to the fact that the sections 35a and 35h of thepreheater have been energized, and the current is substantiallyconstant, a greater amount of heat is liberated by the preheater thanwhen the section 35a is energized alone. This will serve to mediumdurafurnace equiptablished, as shown at the This permits current tosupply through the bar lower right of Fig. 3- pass from the source of42, reed 43. contacts 44h, screw 4Gb, terminal post 48h, throughconductor 02 to the outer end o! the preheater section 35e of the roomthermostat. The entire preheater unit is then energized, including allits sections 35a, 35h and 35C, and if the room thermostat is closed, asshown in will be completed by its return thermostat, the conductor 63,source i0. The energizing of the entire preheater enables it to developits maximum heat. so that the operating cycles of the associated furnaceequipment are of the shortest duration.

By the use of these combined thermostatic controls, the operation of anystandard house through the room motor 3 and t0 fluctuations. Theconstruction avoids any tendency on the part of the furnace to overheat,since when the temperature surrounding the furnace reaches a definitemaximum value, the downward deflection of the bar 42 breaks themotor-operating circuit. Also, if the temperature around the furnaceshould cool suiiciently to permit engagement between contacts 44 andscrew 46, but if the outdoor temperature should be sufiiciently mild sothat furnace operation would not be justied, the operation of thefurnace is prevented by the element 55 maintaining spaced relation fromthe Contact 53. By the inclusion of the sectional preheater in thethermostatically controlled circuits set forth, proper control isreadily obtained over the duration of the operating cycles of thefurnace, providing short, medium and long periods of operation,depending upon prevailing temperature conditions.

Iclaim:

carried by the defiectable end of the second element, a plurality ofspaced stationary contact devices mounted adjacent to said spring memberand adapted to be engaged sequentially thereby upon unidirectionaldeflection of said and means electrically uniting said contact deviceswith the sections of said resistance means operative to energize saidmeans Fig. 1, the circuit sectionally and collectively to vary theliberation oi' heat therefrom. 2. Apparatus for second temperaturedeectable bimetallic element dis bimetallic element of the generatorupon undirectional ment carrying a plurality of spaced contacts at itsfree end, a plurality of cooperative adjustable stationary contactsadapted for sequential engagement with the contacts of the bimetallicelement of the generator thermostat, an outdoor thermostat embodying adefiectable bimetallic element, a plurality of stationary adjustablecontacts positioned in cooperative relation with the bimetallic elementof the outdoor thermostat, conductors extending from the stationarycontacts of the generator and outdoor thermostats to the sections ofsaid heating resistor of the room thermostat, and conductors extendingfrom the Iliimetallic element of the room thermostat to thecorrespondingk element of the furnace thermostat, said power-supply unitfor the heat generator being disposed in the last-named conductors.

6. Thermostatic apparatus lfor controlling the operation of heatingsystems comprising a bimetallic element movably deiiectable in itsresponse to temperature variations, a localized heating unit :forsupplying said element with artiiicially created heat, said unitembodying a.

sectional electrically energized resistance means, Y

a second temperature deflectable bimetallic element disposed remotely tosaid first-named element, a spring member carried by the de'ectable endof the second element, a plurality of spaced stationary contact devicesmounted adjacent to said member and adapted to be engaged sequentiallyupon unidirectional deflection of said second bimetallic element, meanselectrically unit-A ing said contact devices with the sections of saidresistance means for selectively energizing one or more of saidsections, current conductors leading from the first to the secondbimetallic eleaoY Y* Number ments, and aninduction motor disposed insaid last-named conductors, said motor having a pair of fixed shadingcoils and a pair of opposed Wound, shading coils of greater shadingcapacity than the iixed shading coils. v

7. Furnace control apparatus comprising a bimetallic element movablydeiiectable in response to temperature variations adjacent the same, astationary contact engageable with said element when the latter is inone of its operative positions, a localized heating unit for supplyingsaid element with artificially created heat, said unit embodying anelectrically energized sectional resistance means, one terminal of saidresistance means being electrically connected with said contact device,a second thermostat disposed in the zone of heat influence of the heatgenerator of said heating system, current conductors extending from saidbimetallic element to said second thermostat, an electrically actuatedpower supplying unit for increasing or decreasing the heat output of thegenerator arranged in said lastnamed conductors, and a plurality ofindependent current conductors extending from said generator thermostatto the different sections of said resistance means.

GEORGE W. CRISE.

REFERENCES CITED The following references are of record in the ille ofthis patent: v

UNITED STATES PATENTS Name Date 2,288,843 Roland July '7, 1942 2,249,215Lange July 15, 1941 2,262,341 Shaw Nov. 11, 1941 1,883,915 Shipley Oct.18, '1932 1,997,559 Hajek Apr. 9, 1935 1,402,417 Hamilton Jan. 3, 1922

